Stabilized chlorine containing polymers



Patented Dec. 9, 1947 STABILIZED cnLonrNr: CONTAINING POLYMERS GeorgeLowrance Dorongh, Niagara Falls, N. Y.,

assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Dele- No Drawing. Application February 25, 1944,

' Serial No. 523,937

14 Claims. (Cl. 260-485) This invention relates to new compositions ofmatter and more particularly to chlorine-containing polymer compositionswhich are resistant to the effects of light and heat.

Various chlorine-containing polymers have found wide commercial use infilms, fibers, spinning, coating compositions for fabric, and in theproduction of shaped articles by molding ,or extrusion. In general,these chlorine-containing resins, as exemplified by polyvinyl chloride,copolymers of vinyl chloride and similar chlorine.- containing vinylpolymers, have only moderate resistance to the deteriorating effects ofheat and light. For example, severe exposure to heat and/or lightusually brings about discoloration accompanied by loss of strength andtoughness that seriously hampers the use of these materials for manyapplications. This is particularly true for the fabrication of articlesby injection molding. calendaring, or extrusion operations which requireheating the plastic composition for some time at temperatures above itssoftening po nt. In adition, when these resins are exposed to heatand/or light, substantial amounts of hydrogen chloride are oftenliberated, which may attack extrusion or molding equipment or bringabout premature failure of coated cloth due to tendering of the fabricbase.

The invention therefore has as an object to provide chlorine-containingpolymers which are substantially resistant to discoloration anddegradation by the action of heat and/or light. Other objects will beapparent from the description given hereinafter.

These objects are accomplished by the invention of compositionscomprising a chlorine-containing polymer and as a stabilizer againstdeterioration by light and heat an aliphatic mercapto alcohol.

In the practice of this invention, stable chlorine-containing polymersare produced by blending appropriate amounts of an aliphatic mercaptoalcohol with a chlorine-containing polymer in any expedient manner. Aparticularly convenient method comprises swelling the polymer with anorganic solvent such as acetone, adding the aliphatic mercapto alcoholto the resulting material, and mixing thoroughly in a Banbury mixer.lasticizers and pigments can be introduced at the same time, and removalof the voltaile solvent can be accomplished either in the mixer or onheated milling rolls. Other methods of blending the polymers andmercapto alcohols, for example, mixing on heated rolls without addedsolvent, will be apparent to those skilled in the art.

The following examples, in which the parts are by weight. furtherillustrate but do not limit the invention.

Example 1 Ten parts of polyvinyl chloride was thoroughly wet with amethanol solution containing 0.2 part of thiosorbitol; After thoroughstirring of the resulting slurry, the methanol was evaporated by a slowcurrent of air and the resulting polymer dried. Sheets were pressed fromthis modified polymer at a temperature of 160 C. and at a pressure ofabout 1000 lbs/sq. in. for 1 minute. The resulting sheet was clear andpractically colorless while a sheet pressed from unmodified polyvinylchloride was dark amber in color.

Example 2 To parts of a copolymer of vinyl chloride with diethylfumarate, prepared by the copolymerization of five parts of diethylfumarate with 95 parts of vinyl chloride in the manner described incopending applications Serial Nos. 427,921, filed January 23, 1942, or458,737, filed Sept. 17, 1942. there was added 1.5 parts of thiosorbitoland 1.0 part of magnesium. stearate. This composition was thoroughlymixed for 30 minutes on a rubber mill heated at a temperature ofapproximately C. The resulting composition was practically colorless,indicating that no de-' composition had taken place. The same copolymercomposition free of mercapto alcohol, underwent discoloration anddecomposition when heated on the rubber mill.

Pigments, plasticizers, or other material can be added to the copolymerduring or subsequent to the milling operation, and the stabilizedcopolymer can be applied to cloth to give a tough coating. Theseproducts compounded as described above are superior in light and heatstability to corresponding polymers having no aliphatic mercaptoalcohol.

In contrast to the superior heat and color stability conferred uponvinyl chloride-diethyl fumarate copolymers by aliphatic mercaptoalcohols, simple aromatic or aliphatic thiols have given markedlyinferior results. These thiols included beta-thionaphthol,heptadecanethiol-l, the dithiol prepared from vinylcyclohexene,dimercaptonaphthalene, and a polyethylene sulfide having terminal thiolgroups.

Example 3 To 8.5 parts of a vinyl chloride copolymer prepared by thevopolymerization of live parts of diethyl fumarate with 95 parts ofvinyl chloride, there was added 0.085 part each of 1.6-dlthiomannitoland magnesium stearate. After thorough 7 mixing, this composition washomogenized on a smooth rubber mill by heating at 155-160 C. for

about three minutes, and removed in the form of a sheet. Films pressedor calendered from this stabilized vinyl chloride copolymer were foundto be colorless and stable.

distributed through the polymer.

, tion of 25-40% by weight of plasticizers-,xsu'ch' as diibutoxyethyl)scbacate, ,dibutyl phthalate,.tricresyl phosphate, methoxymethylacetylricinoleate, etc., which may be readily incorporated intochlorine-containing polymers, or

copolymers, yields pliable compositions suitable for films or forapplications by calendering.technique to fabrics.

Alkaline earth salts of organic aliphatic acids containing more than tencarbon atoms such as magnesium oleate, calcium stearate, calcium 12-ketostearate as described in Examples 2 and 3 may be blended withchlorine-containing polymers in combination with the aliphatic mercaptoalcohols of this invention to effect further improvements in heat andlight stability. The amount of alkaline earth salt of organic aliphaticacid to be used is usually between 0.1 and 5% based on the weight of thechlorine-containing polymers. These compositions which containcombinations of aliphatic mercapto alcohol and alkaline earth salts oforganic aliphatic acids are particularly meful when the compositions aresubiected to high temperature calendering operations.

The aliphatic mercapto alcohol may also be incorporated into thechlorine-containing poly! mer by mixing the polymer with a solution ofthe mercapto alcohol in a solvent which is a nonsolvent for the polymer.Upon evaporation of the solvent, the mercapto alcohol is uniformly Thelower boiling aliphatic alcohols are examples of solvents that can beused for this purpose.

Stabilized coating compositions based on chlorine-containing polymerscan be prepared by dissolving the polymer in a suitable solvent to whichthe aliphatic mercapto alcohol. usually in amounts of 0.5 to 3.0% basedon the weight of the polymer, is added. The resulting solution, eitherwith or without the addition of plasticizers, pigments, dyes, etc., maythen be used for lacquers, spinning of fibers, casting of film, asfabric coating compositions, and other similar applications.

The chlorine-containing polymers coming within the scope of thisinvention include polymers and copolymers of vinyl chloride, vinylchloride polymers which have subsequently been further chlorinated,chlorinated polyethylene, chlorinated rubber, and polymers andcopolymers of vinylidene chloride. Of the copolymers of vinyl chloride,vinyl chloride-vinyl ester copolymers such as vinyl chloride-vinylacetate copolymers and in particular vinyl chloridealpha,beta-butenedioic dialkyl esters have been found to be particularlyeffectively stabilized by an aliphatic mercapto alcohol. The preparationof copolymers of vinyl chloride and certain alpha, beta-butenedioicdialkyl esters e. g. diethyl or dimethyl fumarate or maleate isdisclosed in pending applications Serial Nos. 427,921, and 458,737. I

. Of the aliphatic mercapto alcohols useful for the stabilization of thechlorine-containing polymers there are included mercapto butanols,mercapto propanecliols, and in particular aliphatic mercapto alcoholsobtained by the reaction of an aliphatic hydroxycarbonyl compound withhydrogen and hydrogen sulfide in the presence of a sulfactive catalystas described in the process of copending application Serial No. 357,417,filed September 19, 1940. These include the following compounds:thiosorbitol, thiodextrose, thiolevulose, thiomannose, or similarthiocarbohydrates in which the carbonyl group in an aldose or ketosesugar-is replaced by a, C(SH)H grouping. Other compounds useful asstabilizers of chlorine-containing polymers include aliphatichydroxydithiols such as 1,6-mannitol dithiol and similar compounds. Themercapto polyhydric alcohols are particularly useful.

The stabilizers are preferably used in amount ranging from 0.01 to 5.0%by weight. based on the weight of the chlorine containing polymer.

The compositions of this invention may be used for the preparation ofmolded plastics. coatings, fibers, films, adhesives, etc.

The above description and examples are intended to be illustrative only.Any modification thereof or variation therefrom which conforms to thespirit of the invention is intended to be included within the scope ofthe claims.

What is claimed is:

1. A composition comprising a chlorine-containing polymer which tends toliberate HC] on exposure to heat or light and, as a. stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weightbased on the weight of the polymer, of an aliphatic mercapto alcohol ofat least three carbon atoms.

2. A composition comprising a vinyl chloride polymer and, as astabilizer therefor against deterioration by heat and light, from 0.01to 5.0% by weight based on the weight of the polymer, of an aliphaticmercapto alcohol of at least three carbon atoms.

3. A composition comprising a copolymer of vinyl chloride with analpha-beta-butenedioic acid d-ialkyl ester and, as a stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weightbased on the weight of the polymer, of an aliphatic mercapto alcohol ofat least three carbon atoms.

4. A composition comprising a chlorine-containing polymer whichtends toliberate HCl on exposure to heat or light and, as a stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weightbased on the weight of the polymer, of an aliphatic mercapto polyhydricalcohol.

5. A composition comprising a chlorine-containing polymer which tends toliberate 101 on exposure to heat or light and, as a stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weightbased on the weight of the polymer, of thiosorbitol.

6. A composition comprising a chlorine-containing polymer which tends toliberate HCl on exposure to heat or light and as stabilizers againstdeterioration by heat and light from 0.01

to 5.0 each, based on the weight of the polymer,

of an aliphatic mercapto alcohol of at least these carbon atoms and analkaline earth metal salt of-a fatty acid of more than ten carbon atoms.

7. A composition comprising a vinyl chloride polymer which tends toliberate HCI on exposure to heat or light and, as a stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weightbased on the weight of the polymer, of an aliphatic mercapto polyhydricalcohol.

8. A composition comprising a copolymer of vinyl chloride with analpha-beta-butenedioic acid dialkyl ester which copolymer tends toliberate HC] on exposure to heat or light and, as a stabilizer thereforagainst deterioration by heat and light, from 0.01 to 5.0% by weight,based on the weight of the copolymer, of an aliphatic mercaptopolyhydrlc alcohol.

9. A composition comprising a chlorine-containing polymer which tends toliberate HCl on exposure to heat or light and, as stabilizers againstdeterioration by heat and light, from 0.01 to 5.0% each, based on theweight of the polymer, of an aliphatic mercapto polyhydric alcohol andan alkaline Cfii'i'il metal salt of a fatty acid of more than ten carbonatoms.

10. A composition comprising a vinyl chloride dicthyl fumarate copolymerand, as a, stabilizer therefor against deterioration by heat and light,from 0.01 to 5.0% by weight, based on the weight of the polymer, ofthiosorbitol.

11. A composition containing a copolymer of vinyl chloride with adialkyl ester of a butenedioic acid ester and, as stabilizers againstdeterioration by heat and light, from. 0.01 to 5.0% each, based on theweight of the copolymer, of an aliphatic mercapto polyhydric alcohol andan alkaline earth metal salt of a fatty acid of more than ten carbonatoms. 1

12. A composition containing a copolymer of vinyl chloride with adialkyl ester of a butenedlolc acid ester and, as stabilizers againstdeterioration by heat and light, from 0.01 to 5.0% each, based on theweight or the copolymer, of 1,6-dithioman- 0 Number nitol and magnesiumstearate.

13. A composition containing vinyl chloride homopolymer and, as astabilizer against deterioration by heat and light, from 0.01 to 5.0%,based on the weight of the polymer, of an aliphatic mercapto polyhydricalcohol.

14. A composition containing vinyl chloride homopolymer and, as astabilizer against deterioration by heat and light, from 0.01 to 5.0%,based on the weight of the polymer, of thiosorbitol.

GEORGE LOWRANCE DOROUGH.

file of this patent:

UNITED STATES PATENTS Name Date Stewart July 31, 1945 OTHER REFERENCESBellstein, Haniibuch der Organische Chemie. vol. 1, page 470.

